Hydrophilized antimicrobial polymers

ABSTRACT

A bactericidal or antimicrobial polymeric composition includes a hydrophilic first comonomer copolymerized to a second comonomer to produce a polymeric composition that is more hydrophilic or more bactericidal or antimicrobial in an aqueous solution than either of the comonomers alone. Methods for identifying bactericidal or antimicrobial polymers, methods for rendering materials bactericidal or antimicrobial, and methods for using bactericidal or antimicrobial compositions to kill or reduce bacterial or microbial growth are also described. Applications for the inventive compositions include their use in catheters, stents, medical devices, contact lenses; root canal fillers; fibers; paper; and/or wound dressing.

The present patent document is a continuation-in-part of applicationSer. No. 11/509,915, filed Aug. 24, 2006, which claims the benefit ofthe filing date under 35 U.S.C. §119(e) of Provisional U.S. PatentApplication Ser. No. 60/711,234, filed Aug. 24, 2005. All of theforegoing applications are hereby incorporated by reference.

BACKGROUND

There is an ever-growing demand for materials suitable for killingharmful microorganisms. Such materials could be used to coat surfaces ofcommon objects touched by people to render them antiseptic so as toprevent transmission of bacterial infections or to facilitate thekilling of microorganisms in solution.

Various polycations are known to have bactericidal properties. However,their bactericidal properties can be strongly influenced by whether thepolycation or a composition containing the polycation is soluble. Insome instances the bactericidal property is most apparent in aninsoluble form, which is not particularly amenable to killingmicroorganisms. In other instances the bactericidal activity is lostwhen the polycation is cross-linked or otherwise rendered insoluble.Application of bactericidal polymers may also be limited by their use inbrushes, their insolubility in solution, or by their unfavorablebiocompatibility characteristics. Accordingly, there is a need forbactericidal formulations possessing having improved bactericidal,hydrophilicity/wettability and biocompatibility characteristics suitablefor rendering materials or areas bactericidal and for killing airborneand/or waterborne microorganisms.

BRIEF SUMMARY

The present invention is directed to polymeric compositions providingimproved bactericidal or antimicrobial, hydrophilicity/wettability, andbiocompatibility characteristics. In particular, the present inventionprovides a bactericidal or antimicrobial composition, including ahydrophilic first comonomer polymerized to a second comonomer to form apolymeric composition, where the polymeric composition is more solubleand/or more bactericidal or antimicrobial in an aqueous solution thaneither of the first comonomer or the second comonomer alone.

In a particular example, the present invention provides a quaternizedbactericidal or antimicrobial composition, in whichpoly(4-vinylpyridine) (PVP) is copolymerized withhydroxyethylmethacrylate (HEMA) or poly(ethyleneglycol) methacrylate(PEGMA).

In another example, the present invention provides an aqueouscomposition comprising a polymeric composition formed from a hydrophilicfirst comonomer polymerized to a second comonomer; and water. The secondcomonomer comprises polycationic species, polycationic derivatives orcombinations therefrom. In some aspects the composition furthercomprises a netural thickener or cationic thickener. In some aspects,the polymeric composition is more hydrophilic than either of the firstcomonomer or the second comonomer alone and/or where the polymericcomposition is more bactericidal or antimicrobial than either of thefirst comonomer or the second comonomer alone. Preferably thehydrophilic first comonomer comprises hydroxyethylmethacrylate orpoly(ethyleneglycol) methacrylate; the second comonomer plurality ofquaternary ammonium groups, more preferably quaternizedpoly(4-vinylpyridine); and the thickener is selected from the groupconsisting of natural gums, pectins, alginates, gelatins, carageenans,flours, starches, dextrins, casein, cellulose derivatives, polyvinylpyrrolidones, polyaminoalkyl methacrylates, and polyaminoalkylacrylates, preferably a cellulose derivative, more preferablyhydroxyethyl cellulose.

In another example, the present invention provides a method forrendering a material or area bactericidal or antimicrobial in which abactericidal or antimicrobial composition of the present invention isapplied to a medium or device in an amount suitable for killing orsignificantly reducing the number of bacteria or microorganisms in or onthe treated medium or device compared to an untreated medium or device.

In another example, the present invention provides a method for killingor significantly reducing the number of bacteria or microorganisms on amaterial or area treated with a bactericidal or antimicrobialcomposition of the present invention.

In a further example, the present invention provides a method foridentifying a polymer having suitable bactericidal or antimicrobialactivity in which a hydrophilic first comonomer is polymerized to asecond comonomer to form a bactericidal or antimicrobial polymericcomposition, where the polymeric composition is determined to havesuitable bactericidal or antimicrobial activity if the polymericcomposition has a higher bactericidal or antimicrobial activity in anaqueous solution than either of the hydrophilic first comonomer orsecond comonomer alone (or treated similarly as the polymericcomposition).

In yet another example, the present invention provides an articlecomprising a polymeric composition posited on a surface of a medium. Thepolymeric composition is formed from a hydrophilic first comonomerpolymerized to a second comonomer. The hydrophilic first comonomercomprises a methacrylate comonomer. The second comonomer comprisesquaternized poly(4-vinylpyridine). The medium is selected from the groupconsisting of catheters, needles, sutures, stents, implantable medicaldevices, contact lenses, root canal fillers, wound dressings, burndressings, tissue culture plates, fibers and paper. Preferably thehydrophilic first comonomer is poly(ethyleneglycol) methacrylate orhydroxyethylmethacrylate and the medium is fibers or paper.

Applications for the inventive compositions include their use incatheters, stents, fibers, paper and other implantable medical devices,contact lenses, root canal fillers, wound dressings, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic showing (A) the radical polymerization ofP(VP-co-HEMA) and (B) quaternization of P(VP-co-HEMA)-HB.

FIG. 2 is graph of bactericidal results for surface testing ofP(VP-co-HEMA)-HB.

FIG. 3 is a graph of advancing and receding contact angles forP(VP-co-HEMA).

FIG. 4 is a graph of bactericidal results for testing ofP(VP-co-PEGMA1100).

FIG. 5 is a graph of dead epithelial cells as a function of PPEGMA,P(VP-co-PEGMA) or control polymer.

DETAILED DESCRIPTION

In order to provide a more clear and consistent understanding of thespecification and claims, the following definitions are provided. Unlessdefined otherwise, all technical and scientific terms have the samemeaning as is commonly understood by one of skill in the art to whichthis invention belongs.

The term “monomer” refers to a relatively simple compound, usuallycontaining carbon and of low molecular weight, which can react to form apolymer by combining with itself or with other monomers.

The terms “polymer” and “polymeric composition” are used interchangeablyto denote a product of a polymerization reaction, and are inclusive ofhomopolymers, copolymers, terpolymers, etc.

The terms “polymerization” and “polymerization reaction” are inclusiveof homopolymerizations, copolymerizations, terpolymerizations, and thelike, and include all types of copolymerizations such as random, graft,block, and the like. In general, the polymers in the bactericidal orantimicrobial composition on may be prepared in accordance with anysuitable polymerization process, including slurry polymerization,solution polymerization, emulsion polymerization, gas phasepolymerization, and high pressure polymerization processes.

The term “comonomer” refers to a monomer, copolymer, or polymer whichcan copolymerize with itself or with at least one different monomer,copolymer, or polymer in a copolymerization reaction, the result ofwhich can be a polymer, copolymer or polymeric composition.

The term “copolymer” refers to a polymer which can copolymerize withitself or with at least one different comonomer, polymer, or copolymerin a polymerization reaction or it can refer to a product resulting froma polymerization reaction of two comonomers. The copolymer may beidentified or named in terms of the monomer(s) from which the copolymeris produced.

The terms “corresponding comonomer,” “corresponding copolymer,” and“corresponding polymer” are used to relate comonomers, copolymers, orpolymers, respectively, sharing a common set of monomeric units betweene.g., distinct polymeric compositions. The common comonomers,copolymers, or polymer need not be identical in terms of the molecularweight(s) or molar ratio(s) of commonly shared monomeric units.

The phrase “corresponding molecular weight” is used to relate molecularweight(s) of corresponding comonomers, copolymers, or polymers,respectively, in distinct polymeric compositions in which the commoncomonomers, copolymers, or polymers differ from one another by molecularweight(s) or commonly shared monomeric units within the correspondingcomonomer, copolymer or polymer.

The phrase “corresponding molar ratio” is used to relate molar ratio(s)of corresponding comonomers, copolymers, or polymers, respectively, indistinct polymeric compositions in which the common comonomers,copolymers, or polymers differ from one another by molar ratio(s) orcommonly shared monomeric units within the corresponding comonomer,copolymer or polymer.

The term “bactericidal” is used to interchangeably denote any one of thefollowing: (i) a comonomer, polymer, copolymer, polymeric compositionsuitably formulated to kill, reduce the growth, number, viability and/ormetabolic activity of one or more bacteria; (ii) a material, substance,medium, device, or area treated with a bactericidal comonomer, polymer,copolymer, polymeric composition so as to kill, reduce the growth,number, viability and/or metabolic activity of one or more bacteria.

The term “antimicrobial” is used interchangeably denote any one of thefollowing: (i) a comonomer, polymer, copolymer, polymeric compositionsuitably formulated to kill, reduce the growth, number, viability and/ormetabolic activity of one or more bacteria, fungi, protozoans, orviruses; (ii) a material, substance, medium, device, or area treatedwith an antimicrobial comonomer, polymer, copolymer, polymericcomposition so as to kill, reduce the growth, number, viability and/ormetabolic activity of one or more bacteria, fungi, protozoans, orviruses.

The terms “microorganism” and “microbe” are used interchangeably todenote microscopic living organisms including for example, bacteria,fungi, protozoans, and viruses.

The term “aqueous solution” refers to a solution in which water is thesolvent.

The term “medium” refers to a treatable material, treatable substance,treatable device, or treatable area in which “treatable” refers to acapacity to be rendered bactericidal or antimicrobial by a bactericidalor antimicrobial comonomer, polymer, or copolymer. A treatable mediummay have a defined physical form, but may include liquid (e.g., water,aqueous solution) or gaseous materials (e.g., air) also.

The phrases “significantly reducing the growth of bacteria” and“significantly reducing bacterial growth” are used interchangeably todenote one or more of the following conditions, including (i) acondition in which the metabolic activity of at least 50% of themicroorganisms of a particular type exposed to a treated medium isterminated or reduced compared to bacteria of that particular typeexposed to an untreated medium over a fixed period of time; (ii) acondition where there is 50% or less of one or more bacterial typespresent in and/or on a treated medium compared to the number of bacteriaexposed to an untreated medium; and/or (iii) a condition resulting whenone or more types of bacteria adhere 50% less to a treated mediumcompared to an untreated medium. The degree of bacterial growthreduction with respective to conditions (i)-(iii) may range from 50% togreater 99.9%.

The phrase “significantly bactericidal” denotes a comonomer, polymer,copolymer, composition, polymeric composition, material, substance ortreated area in which the bactericidal comonomer, polymer, copolymer,composition, polymeric composition, material, substance or treated areais suitably formulated to significantly reduce the growth, number,viability and/or metabolic activity of bacteria by at least 50%.

The term “biocompatible” refers to a material that is substantiallynon-toxic in the in vivo environment of its intended use, and that isnot substantially rejected by the patient's physiological system (i.e.,is non-antigenic). This can be gauged by the ability of a material topass the biocompatibility tests set forth in International StandardsOrganization (ISO) Standard No. 10993 and/or the U.S. Pharmacopeia (USP)23 and/or the U.S. Food and Drug Administration (FDA) blue bookmemorandum No. G95-1, entitled “Use of International Standard ISO-10993,Biological Evaluation of Medical Devices Part-1: Evaluation andTesting.” Typically, these tests measure a material's toxicity,infectivity, pyrogenicity, irritation potential, reactivity, hemolyticactivity, carcinogenicity and/or immunogenicity. A biocompatiblestructure or material, when introduced into a majority of patients, willnot cause a significantly adverse, long-lived or escalating biologicalreaction or response, and is distinguished from a mild, transientinflammation which typically accompanies surgery or implantation offoreign objects into a living organism.

A bactericidal or antimicrobial polymeric composition of the presentinvention includes a hydrophilic first comonomer polymerized to a secondcomonomer, where the polymeric composition is more soluble and/or morebactericidal or antimicrobial in an aqueous solution than either of thefirst comonomer or the second comonomer alone. The polymeric compositionof the present invention were found to have unexpected hydophilizingand/or wettabiliy properties providing enhanced bactericidal orantimicrobial activity compared to either comonomer alone.

The second comonomer may be inherently bactericidal or antimicrobial orit may be rendered bactericidal or antimicrobial after a subsequent step(e.g., polymerization) and/or chemical modification (e.g.,quaternization) of alkyl groups. Where the polymeric composition isfurther modified by chemical modification, such as quaternization,preferably, the polymeric composition is more hydrophilic and/orbactericidal or antimicrobial than a similarly modified (by e.g.,quaternization) second comonomer alone.

Bactericidal or antimicrobial comonomers or those capable of beingrendered bactericidal or antimicrobial are copolymerized to ahydrophilizing comonomer. Exemplary second comonomers for polymerizationto a hydrophilizing comonomer may include a variety of vinyl monomerscapable of free radical polymerization and/or quaternization.Accordingly, these comonomers may include, but are not limited to, vinylamines, such as N,N-dimethylvinylamine; allyl amines; vinyl esters, suchas vinyl acetate; alkyl acrylates; and vinyl chloride. In a preferredembodiment, a pyridinium-type comonomer, such as vinyl pyridine or4-vinylpyridine, is quaternized after polymerization to a hydrophilizingcomonomer.

The second comonomer composition may include or be chemically linked toa suitable bactericidal or antimicrobial moiety, including, but notlimited to polycationic species, polycationic derivatives orcombinations therefrom. Polycationic species may contain two or morequaternary ammonium groups with a molecular weight ranging from severalhundred Daltons to a few hundred thousand Daltons. The quaternaryammonium groups may be part of a ring or they may be acyclic. Examplesinclude but are not limited to: polyionenes,poly(diallyldimethylammonium chloride), dimethylamine-epichlorohydrincopolymers and imidazole-epichlorohydrin copolymers. Suitablebactericidal or antimicrobial comonomers for use in the presentinvention may include the quaternary ammonium group-containing polymersdisclosed in U.S. Pat. No. 4,482,680, which are incorporated byreference herein.

Polycationic species may contain two or more amine groups. The aminegroups can be primary, secondary, tertiary, or mixtures thereof. Theamine groups may be part of a ring or they may be acyclic. Examplesinclude but are not limited to: polyethyleneimines, polypropyleneimines,polyvinylamines, polyallylamines, polydiallylamines, polyamidoamines,polyaminoalkylmethacrylates, polylysines, and mixtures thereof.

The polycationic species may also be a modified polyamine with at leastone amine group substituted with at least one other functional group.Examples include ethoxylated and alkoxylated polyamines and alkylatedpolyamines. Other suitable bactericidal or antimicrobial comonomers orthose that may be rendered bactericidal or antimicrobial may beidentified and/or used in accordance with the applications andobjectives set forth in the specification and claims.

Quaternization may be carried out using alkylating agents, including butnot limited to alkyl halides (such as hexyl bromide), alkyl sulfonates,alkyl mesylates, alkyl tosylates, or other alkylating agents possessinga suitable leaving group. Quaternization reduces self-polymerization ofthe bactericidal or antimicrobial comonomer upon polymerization with thehydrophilizing comonomer. Quaternization may confer increasedbactericidal or antimicrobial activity and is typically carried outafter polymerization, since quaternized polymers are unpolymerizable.

Quaternized alkyl groups and/or other cationic chains may be attractedto and/or promote interaction and penetration negatively chargedbacterial cell walls on account of their lipophilic nature. Alkyl chainlengths of quaternizing agents and overall hydrophilic/lipophilicbalance may affect bactericidal or antimicrobial activity of thepolymeric compositions of the present invention. Accordingly, thesevariables may be modified to optimize or improve bactericidal orantimicrobial activity of the polymeric compositions.

Hydrophilizing comonomers of the present invention confer increasedwettability or hydrophilicity to one or more surfaces of the polymericcomposition in aqueous solutions, including water. Preferably, thepolymeric composition is more wettable than a bactericidal orantimicrobial comonomer or a comonomer rendered bactericidal orantimicrobial by quaternization, such as poly(4-vinylpyridine). Suitablehydrophilizing monomers or copolymers, may include, but are not limitedto, ethylene glycol (ethylyene oxide); polyethylene glycol derivatives,including poly(ethyleneglycol) methacrylate (PEGMA),poly(ethyleneglycol) acrylate, and vinyl polyethylene glycol; vinylacetate; poly(vinyl alcohol); vinyl pyrrolidone and poly(vinylpyrrolidone); vinyl pyrrolidinone and poly(vinyl pyrrolininone); vinyloxazoline and poly(vinyl oxazoline); vinyl foramide and poly(vinylforamide); hydroxyalkyl acrylates and hydroxyalkyl methacrylates, suchas hydroxyethyl methacrylate (HEMA) and hydroxyethyl acrylate;methacrylamide; acrylamide and methacrylamide based monomers, such asacrylamide, N,N-dimethyl acrylamide, N-ethyl acrylamide, N-isopropylacrylamide, and hydroxymethyl acrylamide; monomers containing one ormore of the following functional groups: hydroxy, amino, ammonium,ether, carboxylate, amide, and sulfoamide groups; and combinations orcopolymers thereof. polyvinyloxazolines

Hydrophilic polymeric compositions and methods for hydrophilizingpolymeric materials, including the use of high energy treatments, aredisclosed in U.S. Pat. Appl. No. 20050008839, the contents of which areexpressly incorporated by reference in their entirety, also may be used.

Preferably, the hydrophilizing comonomer is biocompatible. Standardassays may be utilized to evaluate biocompatibility, including but notlimited to viability/cytotoxicity mammalian cell assays and the like.Representative hydrophilizing comonomers or copolymers includehydroxyethylmethacrylate (HEMA) and poly(ethyleneglycol) methacrylate(PEGMA).

HEMA is widely used in biomedical applications and devices, mostprominently soft contact lenses. HEMA, with 37.8% water per weight, istypical of hydrogels. Preferably, the molar ratio of HEMA comonomer inthe polymeric composition is equal to or greater than about 90 to 1.

PEGMA is a biocompatible polymer which possesses several importantproperties, such as good solubility in both organic and aqueous media,low toxicity, immunogenicity and nonbiodegradability.

Preferably, the molar molecular weight of PEGMA comonomer in thebactericidal or antimicrobial composition is equal to or greater than300, more preferably between about 300 and about 2000, including but notlimited to 1100. Preferably, the molar ratio of PEGMA comonomer in thepolymeric composition is equal to or less than about 10 to 1; equal toor less than about 25 to 1; equal to or greater than about 75 to 1;equal to or greater than about 95 to 1; equal to or greater than about99 to 1.

Hydrophilicity or wettability can be evaluated by any suitablemethodology known in the art, including contact angle testing andtensionometry testing. Contact angle testing of polymeric compositionsmay be carried out by dip coating microscope slides in solutions withcopolymer dissolved in chloroform and methanol and obtaining contactangle measurements using e.g., a Ramé-Hart Advanced Goniometer. Contactangles may be characterized as advancing or receding, the differencebeing whether or not the angle is taken when moving onto a dry surfaceor moving off a wet surface. Advancing angles may be used for surfaceenergy determinations, receding angles for characterizing other surfacecharacteristics.

Polymeric bactericidal or antimicrobial compositions may be renderedhydrophilic by engineering them to have advancing contact angles withwater of less than or equal to about 90 degrees, preferably less than orequal to about 45 degrees, more preferably less than or equal to about30 degrees, less than or equal to 15 degrees after 30 seconds ofspreading.

The disclosed bactericidal or antimicrobial compositions are suitablyformulated to significantly reduce the growth, number, viability and/ormetabolic activity of bacteria or microorganisms. A bactericidal orantimicrobial composition may be formulated to significantly reducebacterial or antimicrobial growth from a treated medium by a factor ofat least 50%. Further, a bactericidal or antimicrobial composition maybe formulated to significantly reduce bacterial or microbial growth froma treated medium by at least 60%, by at least 70%, by at least 80%, byat least 90%, by at least 95%, by at least 99%, or by at least 99.9%.

The bactericidal or antimicrobial composition may be applied as acoating to at least one portion or surface of a medium or medicaldevice, such as a catheter, or an implantable medical device, such as astent. Various methods may be used to apply the comonomers orbactericidal or antimicrobial polymers as a coating to the surface ofthe medical device. Suitable methods for applying coatings may include,but are not limited to the methods disclosed in U.S. Pat. No. 5,509,899and U.S. Pat. No. 6,221,425, the contents of which are expresslyincorporated by reference in their entirety.

Comonomers may be applied to a surface and subsequently polymerized.Alternatively, the bactericidal or antimicrobial polymer composition maybe applied directly to the surface of the medical device. In particular,one or more comonomers or bactericidal polymers may be combined withwater and sprayed onto the medical device. Alternatively, the medicaldevice may be dipped into a solution containing the bactericidal orantimicrobial polymer. The comonomer or bactericidal or antimicrobialpolymer may be present in the solution in an amount from about 50% toabout 98% by weight, particularly from about 70% to about 90% by weight,and applied to the surface of the medical device.

The viscosity of the monomeric or polymeric solution can be adjusteddepending upon the particular application and circumstances. In general,when dipping the medical device into the solution, higher viscositieswill cause more of the bactericidal or antimicrobial polymer to remainon the surface of the device. Thus, if thicker coatings are desired, theviscosity can be increased. The viscosity of the solution can beincreased by minimizing the amount of water in the solution.Additionally, thickeners, such as a polyacrylamide, can be added to thesolution. The viscosity of the solution may also be increased bypartially polymerizing the monomer.

In another example, the present invention provides an antimicrobial orantibacterial composition comprising an antibacterial polymericcomposition and water. Other solvents may be added to the compositionincluding alcohols such as ethanol, for example, if desired, but theaddition of an alcohol is not necessary for the antimicrobial orantibacterial properties of the composition. The antimicrobial orantibacterial composition is preferably in liquid form and may beapplied to the skin of a human or mammal. Because the copolymer of thepresent invention will not evaporate and remains present for some timeafter application, the antimicrobial or antibacterial compositionprovides long-lasting antimicrobial effects. Compositions which makewhich make use of quickly evaporating ethanol for the antimicrobialproperties do not provide long-lasting antimicrobial effects and canalso dry out the skin.

To ease application and improve aesthetics, a thickener or gelling agentmay be added to the composition. Any thickener or gelling agent which iscompatible with the antibacterial or antimicrobial polymeric compositionmay be used. Preferably the thickener is suitable for human or mammaluse, more preferably the thickener is approved by the Food and DrugAdministration (FDA). Without wishing to be bound by theory, theformation of an electrolyte between the antibacterial or antimicrobialpolymeric composition and the thickener diminishes efficacy. Because theantibacterial or antimicrobial polymeric composition comprises apolycation chain, it is desirable to use a neutral or cationicthickener.

Examples of cationic thickeners include for example, aminoalkylmethacrylates, alkylaminoalkyl methacrylates, dialkylaminoalkylmethacrylates, aminoalkyl acrylates, alkylaminoalkyl acrylates,dialkylaminoalkyl acrylates. Preferably the cationic thickener is anaminoalkyl methacrylate, more preferably aminoethyl methacrylate.

Examples of neutral thickeners include natural gums, including forexample carrageenans, acacia, guar, guargum, hydroxypropyl guar, karayagum, kelp, locust beangum, tragacanth gum, xanthan gum, alginates andthe like; pectins; gelatins; flours and starches including for example,oat flour, potato starch, wheat flour, wheat starch, and the like;agars; dextrins; and casein; cellulose derivatives, including forexample, carboxymethyl hydroxyethyl cellulose, cellulose, hydroxybutylmethylcellulose, hydroxyethyl cellulose, hydroxypropylcellulose,hydroxypropyl methyl cellulose, methyl cellulose,microcrystalline cellulose, and the like; and poly(vinyl pyrrolidone).Preferably, the thickener is a cellulose derivative, more preferablyhydroxyethyl cellulose.

The amount of thickener present in the composition depends upon thedesired viscosity of the composition. To achieve the desired viscosity,the thickener may be present in the composition in an amount from about1.3% wt. % to about 25 wt. % of the total composition, dependent on theviscosifying agent or agents chosen.

The antimicrobial or antibacterial composition may be used by itself oras an additive to another product. When used by itself, the compositionis applied to the skin, preferably the hands, in an amount from about 1to about 10 mL, preferably about 2 to about 5 mL. The composition isrubbed over the skin to distribute the composition for absorption ontothe skin.

In another example, the present invention provides articles comprisingan antibacterial or antimicrobial polymeric composition of the presentinvention posited on a surface of a medium. The medium may be anyarticle in which it is desirable to render a surface or part of asurface antibacterial or antimicrobial, including for example,catheters, needles, sutures, stents, implantable medical devices,contact lenses, root canal fillers, wound dressings, bum dressings,tissue culture plates, fibers and paper. The antibacterial orantimicrobial polymeric composition may be posited on a surface byapplying the polymeric composition which comprises water and optionallyanother solvent and allowing the water or other solvent to evaporate.For example, a sheet of paper may be coated by forming a polymericcomposition in water and optionally another solvent which does notdissolve paper, applying the polymeric composition to the entire surfaceof the paper and allowing the water or other solvent to dry, therebyforming a polymer coating over the entire surface of the paper.

Alternatively, the hydrophilic first comonomer and second comonomer maybe grafted to the surface of a medium by plasma grafting and thenquaternized with an alkyl bromide to form the antimicrobial surface. Forexample, 4-vinyl pyridine and poly(ethylene glycol) methyl ethermethacrylate may be grafted to the surface of paper via plasma graftingand then quarternized with bromohexane to form the antimicrobialsurface. In another example, the surface or more specifically papersurface may be acylated by reacting it with 4-bromobutyrylchloride whileimmersed in an appropriate solvent. The polymeric composition, formedfor example, from 4-vinyl-pyridine and poly(ethylene glycol) methylether methacrylate may then be quaternized by the surface alkyl bromidegroups.

The antibacterial or antimicrobial polymeric composition may beincorporated into a natural or synthetic fiber. For example, thepolymeric composition may be incorporated on or into fibers used forclothing or paper. Paper made from such fiber may be suitable as a foodwrapping, part of a temporary wound dressing, as a disinfectant wipe, orfor paper used in medical settings such as doctors' offices andhospitals including magazines.

The polymeric composition may be soluble or insoluble, depending onwhether the desired product should be able to release the antibacterialor antimicrobial polymeric composition or retain the antibacterial orantimicrobial polymeric composition. In some aspects, the polymericcomposition may be temporarily posited on the fibers for release onto adesired surface or into a desired environment at a later time. Forexample, a soluble polymeric composition may be used in a disinfectantwipe. The disinfectant wipe, which may be an alcohol based disinfectantwipe, releases the antibacterial or antimicrobial polymeric compositionto another surface, imparting long-lasting antimicrobial properties tothe applied surface.

In another example, the present invention provides methods for renderinga material or area bactericidal or antimicrobial. In a further example,the present invention provides a method for killing or significantlyreducing the number of bacteria or microorganisms on a material or areatreated with a bactericidal or antimicrobial composition of the presentinvention.

Accordingly, in one example, a bactericidal or antimicrobial compositionof the present invention is applied to a medium or medical device in anamount sufficient to kill or significantly reducing the number ofbacteria or microbes in or on the treated medium compared to anuntreated medium. In a further example, a bactericidal or antimicrobialcomposition according to the present invention is applied to a medium ormedical device in an amount sufficient to kill at least one bacterium ormicrobe or significantly reduce bacterial or microbial growth comparedto an untreated medium.

The bacteria may be Gram-positive or Gram-negative. The bactericidal orantimicrobial composition may be is included in or coated onto acatheter, stent, implantable medical device, contact lens, root canalfiller, or wound dressing. The treated medium may include natural orsynthetic materials, implantable devices, or bodily surfaces. Thetreated medium may be contact with an aqueous environment, such as wateror the inside of a patient or other vertebrate organism. Alternatively,the treated medium may be contact with air or air and/or air bornebacteria in an external environment or an enclosed bodily organ, such aslung.

Biocompatibility may be evaluated by any suitable methodology known inthe art, including one or more viability/cytotoxicity assays known tothose of ordinary skill in the art.

In a further example, the present invention provides a method foridentifying a polymer having suitable bactericidal or antimicrobialactivity. In this method, a hydrophilizing first comonomer may bepolymerized to a second comonomer and a bactericidal or antimicrobialpolymeric composition is formed. The bactericidal or antimicrobialpolymeric composition may be applied to a medium to form a first treatedmedium and the medium may be separately treated with the secondcomonomer used in the first treated medium. The first treated medium andthe second treated medium may be separately contacted with a pluralityof bacteria or microbes. Whether the first treated medium is morebactericidal or antimicrobial than the second treated medium may bedetermined.

In a further example, a first polymeric composition and a secondpolymeric composition differing by molecular weight with regard to oneor more corresponding comonomers may be separately applied to a mediumand tested to identify a polymeric composition having improvedbactericidal or antimicrobial activity.

Alternatively, a first polymeric composition and a second polymericcomposition differing by molar ratio of their corresponding comonomersmay be varied and may be separately applied to a medium and tested toidentify a polymeric composition having improved bactericidal orantimicrobial activity.

In the above disclosed methods, a given polymeric composition may berendered bactericidal or antimicrobial by quaternization afterpolymerizing the hydrophilizing first comonomer to the second comonomer.Accordingly, the quaternized polymeric composition would be deemedsuitable for use in a bactericidal or antimicrobial composition if amedium containing or treated with the quaternized polymeric compositionis more hydrophilic and/or bactericidal or antimicrobial than the samemedium containing or treated with the quaternized second comonomeralone.

Bactericidal or antimicrobial activity may be evaluated using anysuitable testing methodology used in the art, including, but not limitedto, luminescence, optical density, or microscopic evaluation ofbacterial or microbial growth or viability of coated and/or stainedmicroscopic slides, plates or cultures.

The following examples illustrate features in accordance with thepresent invention, and are provided solely by way of illustration. Theyare not intended to limit the scope of the appended claims or theirequivalents.

EXAMPLES

1. Radical Polymerization and Quaternization. Copolymers possessingsuitable bactericidal properties and a suitablehydrophilicity/biocompatibility profile were obtained using aquaternized polymeric composition synthesized from 4-vinylpyridine and abiocompatible, hydrophilic comonomer, such as hydroxyethylmethacrylate(HEMA) or poly(ethyleneglycol) methacrylate.

Copolymers were synthesized by radical copolymerization with AIBN asinitiator. The reactants were stirred at 70° C. for 48 hours underflowing N₂ to prevent oxidation. As the monomer contents were varied,the AIBN proportion was held constant to a massic ratio VP+PEGMA:AIBNequal to 22:1. To investigate the effects of hydrophilization, sevendifferent compositions of VP with PEGMA300, PEGMA1100 and HEMA weresynthesized, containing a molar percentage of VP of 10, 25, 50, 75, 90,95 and 99.

Copolymers were quaternized with a 3-fold excess of hexyl bromide (HB)in a mixture of chloroform and methanol by reflux for 48 hr. They wereprecipitated in hexane, recovered and dried under vacuum. A schematic ofthe radical polymerization and quaternization process can be seen inFIG. 1.

Synthesis of P(VP-co-HEMA), P(VP-co-PEGMA300) and P(VP-co-PEGMA1100) wasfollowed with FTIR and NMR. Spectroscopy showed that the synthesis wassuccessful and that the quaternization went to near completion and thatthe resultant products were relatively pure after work-up.

VP, HEMA and PEGMA were purchased from Sigma Aldrich Co. (Milwaukee,USA). To avoid polymerization through heat or light, these monomers wereinhibited with hydroquinone (HQ), 4-Methoxyphenol (MEHQ), and2,6-di-tert-butyl-4-methylphenol (BHT) respectively. The HQ and MEHQinhibitors were removed by means of trap to trap while BHT was purifiedfrom PEGMA by column chromatography on silica gel (70-270 mesh)stationary phase.

2. Antimicrobial Hand Gel

An antimicrobial polymeric composition is prepared by dissolving thepolymeric composition in water or a mixture of ethanol and water, suchas 70% ethanol/30% water. The thickener is then added, and the resultingmixture is heated with stirring and kept below 70° C. until dissolution.

A P(VP-co-PEGMA300) hand gel was prepared by mixing 0.01 g ofP(VP-co-HEMA) with 10 mL of water. Hydroxyethyl cellulose (0.013 g) wasadded, and the resulting mixture heated to 70° C., then cooled to roomtemperature.

3. Contact Angle and Bactericidal Testing. To evaluate wettability orhydrophilicity, contact angle tests were conducted by dip coatingmicroscope slides in solutions with copolymer dissolved in chloroformand methanol. Contact angle measurements were obtained on a Ramé-HartAdvanced Goniometer.

Bactericidal tests were performed with a small quantity of the bacteriaEscherichia coli O157:H7 in which the lux gene was added forluminescence, which provides a measure of metabolic growth or activity.A sample was taken from a culture and placed in contact with the coatedslides, by means of a pipette. The intensity of the bioluminescence wasrecorded as a function of time for two hours with a photomultipliertube. Reduced bioluminescence correlates with enhanced bactericidalactivity.

4. Bactericidal activity of P(VP-co-HEMA). The results of thebactericidal tests on quaternized copolymers of VP and HEMA are shown inFIG. 2. An initial increase of intensity is observed in the control, dueto the fast growth of the bacteria, called blooming. After approximately19 minutes, the intensity starts decreasing as the bacteria start todie. PVP-HB, known to kill bacteria, prevents blooming, as reflected bythe fact that the intensity never increases by more than 1 percent. Theintensity starts decreasing after only 7 minutes. Since this is muchearlier than the control, the death of the bacteria can be attributed tothe properties of the polymer. An uninterrupted blooming is observed fora slide coated with PHEMA, and the number of bacteria has quadrupledafter two hours, following a lag-log behavior. This indicates that PHEMAby itself is not bactericidal.

P(VP-co-HEMA)-HB 95/5 and P(VP-co-HEMA)-HB 90/10 exhibited enhancedbactericidal activity compared to PVP-HB alone. The luminescencerecorded for P(VP-co-HEMA)-HB 99/1, is similar to, but slightly lessthan that observed for PVP-HB alone. Accordingly, this copolymer, havingone molar percent HEMA, displays properties similar to PVP-HB alone.However, a slide coated with P(VP-co-HEMA)-HB 99/1 kills bacteria fasterthan one coated with PVP-HB.

The wettability of dry, vitreous HEMA-based materials was studied bycontact angle measurements. The results for both advancing and recedingangles are given in FIG. 3. Contact angle measurements showed anincrease in hydrophilicity provoked by the copolymerization. The surfaceenergy was found to be minimal for P(VP-co-HEMA) at 90/10 and slightlyhigher for P(VP-co-HEMA)-HB 99/1. This corresponds to the bactericidalbehavior of the polymers and suggests that the wettability plays asignificant role in the polymer's effectiveness. Being a hydrogelmonomer, HEMA hydrophilizes the copolymer.

Although not wishing to be bound by theory, it is believed that couplinghydrophilization to bactericidal activity in the polymer facilitatesenhances bacterial killing, in part because of the water-loving natureof bacteria: a hydrophilic growth medium is better able to supportuptake and killing by a hydrophilized bactericidal polymer compared toan unhydrophilized bactericidal polymer. It is further believed that thehydrophilized bactericidal polymers of the present invention tounexpectedly possess enhanced biocompatility characteristics, enhancedstabilization of blood cells compared to saline and decreased absorptionto proteins and lipids.

In P(VP-co-HEMA)-HB 90/10, the wettability effect is particularlyevident. This polymer exhibits a more optimal bactericidal activity,reflected in the fact that all bacteria were killed in 30 minutes. Thisfurther illustrates that that a slide coated with P(VP-co-HEMA)-HB 90/10copolymer is significantly more bactericidal than pure PVP-HB.

5. Bactericidal activity of P(VP-co-PEGMA). The bacterial growthbehavior for copolymers with PEGMA1100 can be seen in FIG. 4. Comonomerratios of 90/10, 25/75, and 10/90 exhibited enhanced bactericidalactivity compared to PVP-HB alone. Extremely high bactericidal activitywas seen with ratios of 99/1, presumably due to the large fraction of VPand improved wettability from PEGMA1100. Copolymers with ratios rangingfrom 95/5 to 50/50 displayed bacterial results similar to PVP-HB.

P(VP-co-PEGMA1100)-HB 25/75 and 10/90 displayed a surprisingly highantibacterial activity. Although counterintuitive, this fact can haveseveral explanations. The molecular weight of P(VP-co-PEGMA1100)-HB10/90 is much higher than other copolymer formulations of this system.This could increase bactericidal activity, because the copolymerpossesses more alkyl tails to traverse the bacterial membranes. Theenhanced water wettability of the polymer may enable the polymer tobetter dissolve in and/or surround the bacteria in an aqueous medium, soas to facilitate more efficient bacterial killing.

PPEGMA300 (graph not shown) alone does not kill bacteria and actuallyimproves growth due to its biocompatibility and hydrophilicity. Theimproved biocompatibility and hydrophilicity is carried over into theP(VP-co-PEGMA300) copolymers with ratios from 0/100 to 50/50 therebyimproving bacterial growth. However, for ratios greater 50/50,bactericidal activity was observed. The optimum balance betweenspreading and VP content was found to be 75/25, in which half thebacteria were killed in the first 15 minutes. Overall, the bactericidalbehavior of the PEGMA300 based polymers were reduced compared toPEGMA1100 based polymers.

PEGMA1100 has a significantly larger PEG size than PEGMA300. A smallerfraction of PEGMA1100 is thus necessary to hydrophilizeP(VP-co-PEGMA1100). However, even for some similarly hydrophilizedpolymers, the PEGMA1100 materials exhibit superior bactericidalactivity, possibly due to the enhanced protein resistance imparted bylonger PEG chains in the polymers.

The enhanced bactericidal activity exhibited by the HEMA and PEGMAcopolymers appears to result from enhanced wettability in aqueoussolutions, allowing the polymer to better surround and/or gain access tothe bacteria, so as to enhance bacterial killing.

6. Cytotoxity of P(VP-co-PEGMA). A viability/cytotoxicity assay may beused to evaluate biocompatibility of the bactericidal polymers formammalian cells. In particular, FIG. 5 shows that an exemplarybactericidal PEGMA 1100 copolymer is non-toxic to mammalian cells.Corneal epithelial cells were seeded onto polystyrene culture plates inphosphobuffered saline solution (PBS; pH 7.2) at a density of 3,500cells/cm² for 24 hrs at 37° C. The cells were co-incubated for 4 hrs.with quaternized P(VP-co-PEGMA 1100) copolymer or PPEGMA control polymerin PBS at a concentration of 2.5 mg/ml, along with a PBS negativecontrol media.

Live cells were distinguished from dead cells using a fluorescence-basedLIVE/DEAD viability/cytotoxicity assay system (Molecular Probes,Invitrogen Detection Technologies). The assay system includes twoprobes, calcein AM, a fluorogenic esterase substrate producing a greenfluorescent product in live cells having intracellular esteraseactivity, and ethidium homodimer-1, a high-affinity, red fluorescent dyeonly able to pass through and stain the compromised membranes of deadcells. FIG. 5 plots the fraction of dead epithelial cells as a functionof added bactericidal polymer or polymer control. As shown in FIG. 5,treatment of epithelial cells with the bactericidal P(VP-co-PEGMA)polymer did not exhibit a statistically significant level of epithelialcell killing over that of the PEGMA polymer or PBS negative controls.

It is to be understood that the above-described polymers and methods fortheir use are merely representative embodiments illustrating theprinciples of this invention and that other variations in the polymersor methods, may be devised by those skilled in the art without departingfrom the spirit and scope of this invention. The foregoing detaileddescription and accompanying drawings have been provided solely by wayof explanation and illustration, and are not intended to limit the scopeof the appended claims. Many variations in the presently preferredembodiments illustrated herein will be apparent to one of ordinary skillin the art, and remain within the scope of the appended claims and theirequivalents.

What is claimed is:
 1. A composition comprising a copolymer formed froma hydrophilic first comonomer having an acrylate moiety and a secondpyridinium-type comonomer containing a nitrogen atom and a vinyl moiety,wherein the first comonomer and the second comonomer are chemicallybonded within the copolymer through the acrylate moiety of the firstcomonomer and the vinyl moiety of the second comonomer, wherein saidnitrogen atom is quaternized with an alkyl moiety such that saidcopolymer is polycationic, and wherein the amounts of the firstcomonomer and the second comonomer provide said copolymer with a.improved bactericidal activity as compared to the first comonomer or ahomopolymer formed from the first comonomer; and b. improvedbactericidal activity as compared to the second comonomer or ahomopolymer formed from the second comonomer.
 2. The composition ofclaim 1, wherein the hydrophilic first comonomer compriseshydroxyethylmethacrylate.
 3. The composition of claim 1, wherein thehydrophilic first comonomer comprises at least one of poly(ethyleneglycol) methacrylate and poly(ethylene glycol) methyl ethermethacrylate.
 4. The composition of claim 1, wherein the hydrophilicfirst comonomer comprises poly(ethylene glycol) methacrylate.
 5. Thecomposition of claim 1, wherein the hydrophilic first comonomercomprises poly(ethylene glycol) methyl ether methacrylate.
 6. Thecomposition of claim 1, wherein the second comonomer comprises4-vinylpyridine.
 7. The composition of claim 1 wherein said nitrogen isquaternized with an alkyl moiety.
 8. The composition of claim 1 furthercomprising a halide anion associated with a cation of the quaternizednitrogen of the polycationic copolymer.
 9. The composition of claim 8wherein the anion comprises a bromide anion.
 10. The composition ofclaim 7 wherein the alkyl moiety comprises a hexyl moiety.
 11. Thecomposition of claim 10 further comprising a halide anion associatedwith a cation of the quaternized nitrogen of the polycationic copolymer.12. The composition of claim 11 wherein the halide anion comprises abromide anion.
 13. The composition of claim 1, wherein the hydrophilicfirst comonomer comprises at least one selected from poly(ethyleneglycol) methacrylate, poly(ethylene glycol) methyl ether methacrylate,and hydroxyethylmethacrylate and the second comonomer comprises4-vinylpyridine.
 14. The composition of claim 13 wherein the firstcomonomer comprises poly(ethylene glycol) methacrylate having amolecular weight of at least about 300 Daltons.
 15. The composition ofclaim 14 wherein the molecular weight of said poly(ethylene glycol) isless than about 2000 Daltons.
 16. The composition of claim 14 whereinsaid copolymer contains at least about 1 mol percent of at least oneselected from said poly(ethylene glycol) methacrylate and saidpoly(ethylene glycol) methyl ether methacrylate.
 17. The composition ofclaim 13 wherein the first comonomer comprises hydroxyethylmethacrylate.18. The composition of claim 13 wherein said nitrogen is quaternizedwith an alkyl moiety.
 19. The composition of claim 13 further comprisinga halide anion associated with a cation of the quaternized nitrogen ofthe polycationic copolymer.
 20. The composition of claim 19 wherein theanion comprises a bromide anion.
 21. The composition of claim 18 whereinthe alkyl moiety comprises a hexyl moiety.
 22. The composition of claim21 further comprising a halide anion associated with a cation of thequaternized nitrogen of the polycationic copolymer.
 23. The compositionof claim 22 wherein the halide anion comprises a bromide anion.
 24. Thecomposition of claim 14 wherein the hydrophilic first comonomercomprises poly(ethylene glycol) methyl ether methacrylate.
 25. Thecomposition of claim 24 wherein the alkyl moiety comprises a hexylmoiety.
 26. The composition of claim 24 further comprising a bromideanion associated with a cation of the quaternized nitrogen of thepolycationic copolymer.
 27. The composition of claim 25 furthercomprising a bromide anion associated with a cation of the quaternizednitrogen of the polycationic copolymer.
 28. The composition of claim 1wherein the copolymer is a random copolymer.
 29. The composition ofclaim 1 wherein the copolymer is a block copolymer.